1. Field of the Invention
The present invention is related to a contact for coaxial cable and an end processing method for coaxial cable. Particularly, the present invention relates to a structure of a contact for crimping an inner conductor and a dielectric body provided in a coaxial cable, and an end processing method of coaxial cable using the contact.
2. Related Art
A coaxial cable is an unbalanced shielded wire with characteristic impedance being defined for transmitting an electronic signal. The coaxial cable is characterized by preventing electromagnetic wave leakage to the outside and allowing bend to a certain extent, and is used as a feeder cable that connects a TV receiver, a radio or the like with an antenna.
In the coaxial cable, an inner conductor disposed in a central portion is covered with a dielectric body (insulating body) such as polyethylene. The dielectric body is covered with an outer conductor composed of braided wire, and the outer conductor is further covered with a sheath (protection covering).
In a case of connecting a contact to an end of such a coaxial cable, the contact is electrically connected to the outer conductor using an outer conductor contact having a conductor barrel that crimps the outer conductor and an insulation grip that crimps the sheath.
If a crimping force is high in a case of crimping the outer conductor by the conductor barrel, the conductor is deformed to be squashed and this affects impedance fluctuation during transmission of an electronic signal.
On the other hand, if a crimping force is low in a case of crimping the outer conductor by the conductor barrel, fixing strength between the outer conductor contact and the coaxial cable lowers and this may cause relative drop-off when a tensile force in a direction of separating the outer conductor contact and the coaxial cable is applied.
In order to prevent the abovementioned problems, for example Japanese Patent Application Publication No. 2006-302824 (hereinafter referred to as Patent Document 1) discloses a connector for coaxial cable having an outer conductor contact for crimping an outer conductor by a conductor barrel, in which a cylindrical metallic sleeve is applied to a dielectric body, covered with the outer conductor, and crimped by the conductor barrel.
The sleeve disclosed in Patent Document 1 is characterized in having a portion in which a first end edge of the abutting end edges being a joint in a circumference direction is formed to be a tapered face inclined in a diameter direction so as to climb over the other end edge and a portion which is formed to be a tapered face inclined in a diameter direction so as to slide under a second end edge, in a mixed manner, and the second end edge opposed to the first end edge is formed to be an inverse-tapered face so that it may slide along this tapered face.
Patent Document 1 discloses that such a sleeve can prevent deformation of a coaxial cable for high frequency wave when the outer conductor contact is connected to the coaxial cable, and can provide superior high-frequency response, high wire-fixing strength, and superior electrical connection.
According to a first embodiment of Patent Document 1, an inner conductor contact (inner conductor terminal 20), an outer conductor contact (outer conductor terminal 50), and a sleeve (cylindrical sleeve 30) are configured separately, thereby prolonging end processing step (fabrication time) of the coaxial cable. As a result, it is difficult to reduce production cost of a so-called wiring harness, in which connectors for coaxial cable are attached to ends of a coaxial cable.
According to a second embodiment of Patent Document 1, although an outer conductor contact (outer conductor terminal 51) and a sleeve (cylindrical sleeve 30) are integrally composed, a shell (separate shielding member 58 with a shield conductor crimp part 54 and a sheath crimp part 56) is required for connecting the outer conductor contact (outer conductor terminal 51) and a braided wire (shield conductor 16).
As a result, as in the first embodiment, it is difficult to reduce production cost of a so-called wiring harness, in which connectors for coaxial cable are attached to ends of a coaxial cable.
In addition, in the first and second embodiments of Patent Document 1, since the inner conductor contact (inner conductor terminal 20) and the sleeve (cylindrical sleeve 30) are configured to be separately attached, an attachment position, relative to the inner conductor contact, of the sleeve to the dielectric body (insulating body 14) is uncertain. If the sleeve cannot be attached to a specific position relative to the inner conductor contact and dislocation variation is great, a voltage standing wave ratio (VSWR), which is a designed value, varies due to signal reflection. If the VSWR is high, transmission failure such as noise may be caused on a reception side.